Scoville Scale

The Scoville Scale, or Scoville Heat Units (SHU) is what we use to measure the potency of chilli peppers, or more specifically, the concentration of the capsaicin molecule.

The original test invented in 1912 by Wilbur Scoville is seen as inaccurate by modern times due to the subjective nature of using human testers. It comprises of dissolving dried pepper in alcohol to draw out the heat components of the chilli, and then diluted in a sugar water solution. The solution is then given to a team of five testers in decreasing concentration until the majority can no longer detect any heat levels. The ratio of the dissolved chilli to sugar water solution becomes the chilli’s SHU rating.

For example, a Jalapeno with a 5,000 SHU would take approximately 5 litres of sugar solution to no longer detect 1g of (dried) dissolved chilli.

Modern day tests are much more scientific in it’s approach by using high-performance liquid chromatography (HPLC) to determine where on the Scoville Scale a given chilli lies.

High-performance liquid chromatography is a technique in analytical chemistry used to separate, identify, and quantify each component in a mixture

HPLC results enable use of a mathematical formula that weights them according to their relative capacity to produce perceived heat (“pungency”). This method yields results in American Spice Trade Association (ASTA) “pungency units” which are defined as one part capsaicin per million parts dried pepper mass. The number of pungency units is then multiplied by 15 to produce a Scoville score.